Climate Change · Part One
Climate Change · Part Two
Introduction to Astronomy
Life in the Universe
Glossary: Climate Change
Glossary: Life in Universe
Glossary of Terms - M to R
Index: A to F | G to L | M to R | S to Z
Manabe, Syukuro -
(born 1931): Japanese climatologist and a pioneer of mathematical climate modeling as applied to the climate change from the increase of carbon dioxide in the atmosphere. He also succeeded in estimating the contribution of atmospheric water vapor in enhancing the greenhouse effect and applying climate models to the reconstruction of past climate. He is currently director of the Global Warming Research Program in Japan.
Mass Units - (n.)
When dealing with the enormous quantities of carbon discussed in global climate change studies, scientists use the following units:
tonne: a unit of weight equal to 1000 kg (103 kg).
kt: kilotonnes; equal to 1000 tonnes or 106 kg.
GtC: gigatonnes of carbon; 1 GtC is equal to 109 tonnes of carbon or 1012 kg. 3.7 Gt carbon dioxide will give 1 GtC. To give you an idea how big this unit is: in 1997 the total supply of petroleum for the USA (including imports) was approximately 1 Gt per year.
TgC: teragrams of carbon or 1012 grams of carbon.
PgC: petagrams of carbon or 1015 grams of carbon; 1 PgC is equal to 1 Gigatonne of carbon.
Maunder, Edward Walter -
(1851-1928): British astronomer who tied historic observations to reduced sunspot activity between 1645 and 1715, a period is now known as the "Maunder minimum” which occurs in the central portion of the "Little Ice Age," a time with an increased abundance of cool summers and exceptionally cold winters in Europe.
Maury, Matthew Fontaine -
(1806-1873): American oceanographer and director of the U.S. Naval Observatory and Hydrographic Office. He is most famous for his handbook on ocean currents, compiled from information supplied by merchant ships, which was very popular with seagoers and went through many editions.
Methane clathrate, methane hydrate or methane ice - (n.)
In the presence of high concentrations of certain gases in the water, at low temperatures and high pressures, "clathrates" can form: open-structured water ice hosting gases such as methane, carbon dioxide or hydrogen sulfide. Methane clathrate is such an icy compound where the trapped gas is methane. One unit of ice, by volume, can contain as much as 164 units of methane gas, by volume. Methane ice is present in permafrost regions in Siberia and North America and is widespread on the seafloor in the vicinity of continents, below regions of high productivity, at depths of more than 300 m and temperatures near freezing. When methane is formed by bacterial decay within organic-rich sediments in, it rises to escape into the water. As it rises, it enters into a colder zone, since heating within the Earth produces a temperature increase downward within the sediment. When the stability zone (lying somewhat below the seafloor within the sediment) for methane clathrate is reached it forms, thereby trapping the gas underneath. This typical sequence — a layer of gas-rich sediment below a layer of ice-rich sediment — provides a strong reflector for sound. When sending sound waves from a ship and listening to the return, within the sediment (a technique called "acoustic profiling") this strong echo layer is readily recognized, as a "bottom-simulating reflector" or "BSR." In this fashion, methane ice distribution has been mapped worldwide. In places, methane ice has been recovered by dredging or drilling, and thus its properties are quite well known. Methane clathrate can also be made in the laboratory.
Methane ice may be involved in the fluctuations of atmospheric methane seen in polar ice cores. From this record, it is known that methane rose rapidly whenever climate changed from glacial to interglacial conditions (during "deglaciation"). Warming of water bathing the seafloor could have led to large-scale release of methane from the melting of methane ice. Evidence for such a process is seen on the floor of the Barents Sea, which is the shelf sea north of Norway and forms part of the Arctic. Fields of giant craters have been detected within that sea off the coast of Norway, in a region rich in methane clathrate deposits. The biggest of the craters was measured as 700 m wide and 30 m deep, indicating catastrophic explosions of methane. It is thought that these craters were formed during deglaciation. Direct measurements show that large amounts of methane can escape from the Sea of Okhotsk on occasion, where the seafloor is rich in organic matter and harbors methane ice. Pressure is increased on the seafloor during deglaciation (from the rise in sea level). Thus, if the seafloor is the source of the methane increase seen in ice cores, a marked rise in temperature must be responsible for release of methane. This would imply that intermediate waters must have been considerably colder than now, during glacial time. Also, the contribution of large amounts of methane would provide an additional source for the increase of carbon dioxide observed during deglaciation. Evidence for catastrophic release of methane has been found in the more distant geologic record as well, within deep-sea sediments, for a period at the end of the Paleocene about 55 million years ago. The event led to widespread extinctions in the fauna living on the deep-sea floor.
Some good references on methane clathrates: Flammable ice. by E. Suess, G. Bohrmann, J. Greinert and E. Lausch. Scientific American, 281 (5) 76-83, 1999; Probing Gas Hydrate Deposits. By Robert Kleinberg & Peter Brewer. American Scientist, Vol. 89 (No. 3) 2001; Gas hydrates: relevance to world margin stability and climate change. Edited by J.-P. Henriet and J. Mienert. Geological Society Special Publications, vol. 137, 1998; Potential effects of gas hydrate on human welfare. by K. A. Kvenvolden, in Proceedings of the National Academy of Sciences USA, Vol. 96, 3420-3426, 1999.
Mixed layer - (n.)
The uppermost layer of the ocean containing the surface waters. It is mixed by the wind and its thickness ranges from about 10 m, in upwelling regions, to 150 m, in regions where warm water converges.
Monsoon - (n.)
The word monsoon comes from an Arabic word meaning “season.” Monsoon winds are giant sea and land breezes produced by the seasons. Summer is analogous to daytime, and winter corresponds to nighttime. Summer monsoons, in essence a giant sea breeze, bring moisture and rainfall. Winter monsoons, in contrast, tend to bring drought. The strongest monsoonal patterns are in the tropics, with the Indian monsoon being the outstanding example. The seasonal winds within this system extend over East Africa, Arabia, India, and the Arabian Sea. Their existence has been known for a long time: an Arab navigator used the summer monsoon to speed Vasco da Gama from East Africa to India, in 1498. The summer monsoon in India is a product of the low pressure zone which begins to form early in summer, over the Asian highlands. Following the Sun's apparent path to the north, the southwesterly winds appear first in Ceylon, at the end of May, and arrive at the foot of the Himalayas in July. Here they drop an enormous amount of rain, up to several meters in three months. The winter monsoon in the region is essentially indistinguishable from the easterly trade wind pattern that is normal for this region. The West African monsoon also is well known. Summer winds bring rain to the forests and savannas south of the Sahara (Sahel), from the Gulf of Guinea. Winter produces the dusty, dry Harmattan which blows from east-northeast and brings red dust into the Atlantic (along with the occasional locust). Monsoonal winds also occur in North America, in the Gulf region. In summer, low pressure regimes commonly develop over the heated land, and humid marine air may then be pulled in from the southeast, across Texas. During winter, northeastern winds are quite frequent, generated by the high atmospheric pressure over the cold interior. These monsoonal influences, however, are commonly masked by the complexities of mid-latitude air circulation. Here the air flow is dominated by the interaction between polar and tropical air masses (polar front) producing cyclones. See also "cyclones.”
Montreal Protocol - (n.)
a landmark international agreement designed to protect the stratospheric ozone layer. The treaty was originally signed in 1987 and substantially amended in 1990 and 1992. The Montreal Protocol stipulates that the production and consumption of compounds that deplete ozone in the stratosphere (chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform) are to be phased out by 2000 (2005 for methyl chloroform). Once emitted to the atmosphere, these compounds significantly deplete the stratospheric ozone layer that shields the planet from damaging UV-B radiation.
Munk, Walter -
(born 1917): Austrian-American oceanographer and currently a professor of oceanography at Scripps Institution of Oceanography, UC San Diego. He received his Ph.D. in 1947 at UCLA with Harald Sverdrup (see entry below) as his advisor and served as director of the Institute of Geophysics and Planetary Physics from 1960 to 1982 at Scripps Institution of Oceanography. His major contributions are to the understanding of ocean circulation, waves and tides. He is also co-originator of the ATOC project, a large-scale experiment that began in 1995 to measure the warming of the ocean by recording changes in sound velocity within it over large distances.
Newell, Reginald E. -
American climatologist and pioneer in modeling climate change, currently at MIT (Massachusetts Institute of Technology). His work includes the generation of global data sets for studies of global warming; the influence of volcanic activity on global temperature; sea-air interaction using ocean and satellite data; and the global oceanic and atmospheric energy balance.
Index: A to F | G to L | M to R | S to Z
Newton, Sir Isaac -
(1642-1727): English physicist and mathematician. He was also a bible scholar and was given the post of “Master of the British Mint” in 1695. Considered by many to be one of the greatest scientists who ever lived, Newton discovered the laws of gravity and explored the nature of light. He invented calculus independently of Gottfried Leibniz (1646-1716). He formulated the basic laws of physics, fundamental to celestial mechanics, which describe the
gravitational attraction between two bodies (i.e. product of masses divided by square of distance). One of his most important books was Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy first published in 1687. This text contains the three laws of motion: a body at rest or in uniform motion will retain that state unless a force is applied; force equals the mass of a body multiplied by the acceleration produced by application of the force; if a body exerts a force on another, that body exerts an equal and opposite force on the first body. Newton used these laws to explain a wide variety of motions, from the Moon and planets to tides. Newton's laws are an integral part of describing all motions on Earth, including winds and ocean currents.
Nordic heat pump - (n.)
The Nordic heat pump is a feature associated with the production of North Atlantic Deep Water, made in the regions east and west of southern Greenland. Here surface water is cooled and sinks after it has given up much of its heat. It is then replaced by more warm water from the south. Cold deep water is exported from the region in return for the warm water imported. This process helps stabilize the Iceland Low, which in turn helps drive warm winds into the northern North Atlantic. See also “Atlantic Heat Conveyer.”
Normal distribution - (n.)
In statistics, a normal distribution of a population of values follows the equations given by the mathematician Gauss, whereby a decreasing probability of occurrence is ascribed to values with increasing distance from the mean. This distance is measured in terms of "standard deviation." About 68 percent of a given population of numbers in such a distribution are within one standard deviation about the mean. The proportion of values within two standard deviations of the mean is 95.5%. The proportion of values within three standard deviations of the mean is 99.7 percent. Many properties of commonly observed classes of objects follow the normal distribution, including: the weight of house cats in San Diego, the number of minutes it takes to commute to work, the number of miles obtained per gallon of fuel for cars on the freeway, the number of phone calls coming in to the University on Thursdays, or the number of points made by a given basketball team in a given year. If the observations change their mean or standard deviation through time, disturbing factors are suspected; for instance, in reference to the previous examples: the distance between home and office changed, people bought more trucks and SUV’s, people switched to cell phones, or the team lost its best player to injury during the middle of the year. Mathematical statistics, by comparing distributions, can help determine whether a change has indeed occurred, or whether a perceived change is more likely within the range of normal variations. Ultimately, statistics answers the question: If I say there is a change, what is my chance of being wrong?
Oeschger, Hans -
(1927-1998): Swiss physicist and climatologist. A major figure in the reconstruction of climate change from Greenland ice cores, he discovered that there was a large change in carbon dioxide between the glacial and postglacial time, independently of Claude Lorius who made the same discovery.
Output - (n.)
Amount of matter exiting an Earth biogeochemical reservoir per unit time. In geochemical models, the output is usually taken as equal to the input, which is the necessary condition for keeping a reservoir constant in size.
Oxygen isotopes - (n.)
Among the most commonly studied stable isotopes in climate research are those of oxygen, especially the ratio between oxygen-16 (the common atom) and oxygen-18 (the rarer form). Water containing oxygen-18 (or deuterium) enters the vapor phase less readily than normal water with an oxygen-16 atom and two hydrogen atoms. Also, the water with a heavier isotope condenses more easily from vapor during precipitation as rain or snow. Thus, the distribution of these isotopes in natural waters (including the ocean) reflects evaporation and precipitation processes (and, in the oceans, the motion and mixing of different water masses). The precipitation history of a parcel of air with its associated vapor is largely controlled by temperature changes. Thus, the ratio between heavy and light isotopes of hydrogen and of oxygen in polar ice can be used to reconstruct the temperature of the precipitation of snow on a given glacier. In the reconstruction of ice age cycles, the content of oxygen-18 within the shells of foraminifers (small one-celled organisms) has proved crucial. The ratio of 18O to 16O (expressed as the deviation δ from the ratio in a standard: δ18O = [sample ratio]/[standard ratio]-1) changes in marine carbonate shells as a function of both the temperature of the water in which the shells (made of CaCO3) are precipitated, and the amount of water that has been extracted from the ocean and locked up in polar ice. The polar ice is enriched in oxygen-16 relative to the ocean, and thus the ocean is enriched in oxygen-18 whenever ice shields are large. Maximum polar ice buildup during the last several hundred thousand years changes the ocean's delta value by about 1.2 ‰ (or 0.12 percent), corresponding to a change of 0.1 ‰ for each 10 m of sea level change. The portion of a change in isotope ratio that is due to temperature change follows the rule that 0.2 ‰ of change in the delta value corresponds to a change in temperature of 1°C. (‰ is the symbol for permil, in contrast to %, the symbol for percent.)
Penck, Albrecht -
(1858-1945): German geologist. He mapped the moraines and gravel deposits in the periphery of the Alps and related them to major glaciations. He rejected cyclicity and astronomic forcing as important aspects of ice-age climates. His major work, written with E. Brückner, was Geologie der Alpen (Geology of the Alps).
Permafrost - (n.)
A permanently frozen layer of soil, often hundreds of meters thick, found in the polar tundra. In the summer, the upper layer of the permafrost melts, resulting in muddy, swampy conditions. There is concern among climatologists that the increased temperature resulting from global warming will melt much of the Earth’s permafrost, with severe implications for soil stability and tundra ecology. See also “thermokarst.”
Pettersson, Hans -
(1888-1966): Swedish oceanographer. He led the Swedish Deep-Sea Expedition of 1947-1948, a circumnavigation of the Earth that was the first systematic collection of long cores from the seafloor. This expedition resulted in a new understanding of the ocean's role in creating ice-age climate.
Philander, S.G.H. -
American climatologist and physical oceanographer. He is leader in research on the ENSO (El Nino, Southern Oscillation) phenomenon.
Index: A to F | G to L | M to R | S to Z
Photosynthesis - (n.)
Process carried out by chlorophyll-bearing organisms whereby carbon dioxide and water are converted into living organic matter, using nutrients, trace elements and sunlight.
Phytoplankton - (n.)
Microscopic photosynthesizing organisms adrift in the sunlit surface waters of the ocean. The most important types of phytoplankton are "diatoms" and "dinoflagellates." Diatoms have shells made of silica (precipitated from silicate in seawater) and built on the pillbox principle. Diatoms are ubiquitous, but are most abundant in upwelling regions. Dinoflagellates have cell walls made of organic matter, and a tail, called a "flagella," which is used to move the organism through the water. Both diatoms and dinoflagellates are unicellular organisms.
Pollard, D. -
American geophysicist at Oregon State University. He gave a correct time scale for the ice age history of the last million years by creating a model that combined Milankovitch Theory with isostatic bedrock response and ice-sheet calving.
Pratt, John Henry -
(1809-1871): British geophysicist. He proposed "isostasy," the principle that mountains are high because they have deep roots of less dense material than the upper mantle that provide for a gravitational force corresponding to the difference in weight of root and mantle material. Isostasy is important in modeling ice age climate because the buildup and decay of large ice masses changes the elevation of the continental crust that bears the ice.
Productivity - (n.)
The amount of carbon fixed by photosynthesis in the uppermost layers of the ocean. Radiocarbon measurements suggest a total productivity of 30 billion tons of carbon per year. About half of this is fixed within a few hundred kilometers of the coast, the "green" coastal ocean, and the rest is found in the vast expanses of the "blue" ocean. This pattern reflects the fact that vertical mixing is greatest in the coastal ocean. Along many coastlines, also, there is a strong upward motion of cold deep waters from the thermocline, called "coastal upwelling." Strong seasonal coastal upwelling occurs off the shores of California (where this cold upwelling water makes surfers wear wetsuits), off Peru, off northwestern Africa, off Namibia, and in the Arabian Sea. In these areas productivity is especially high and fish are potentially plentiful. There is one important exception to this overall blue-ocean/green-ocean dichotomy: a strip of high productivity along the equator. The equatorial upwelling results from effects introduced by the rotation of the Earth, on the motion of water masses driven westward by the trade winds. It is especially strong in the eastern equatorial regions of the Pacific and the Atlantic, and high-sea fisheries are correspondingly intense in these regions.
Proxy - (n.)
In paleoclimatic reconstruction, a proxy is a measure of climate conditions of the past. A proxy (or proxy variable) yields clues as to temperature, precipitation, productivity, or other environmental conditions. Examples of proxies are: presence and absence of fossils; the abundance ratios of fossils; and the chemical composition of fossils, growth rings of trees and corals. Proxies can be classified according to the type of properties of a sediment they describe (physical, chemical, isotopic, or biological remains) or according to the target which they are supposed to represent. The first approach equates proxies (correctly) with sediment properties (e.g. oxygen isotope ratio in fossil shells). The second approach emphasizes climate-relevant parameters, such as temperature. Thus, in the case where proxies are classified by the targets they are thought to represent, we speak of temperature proxies, sea-level proxies, and rainfall proxies.
Punctuated equilibrium - (n.)
Proposition regarding evolution of life introduced by paleontologists Nils Eldredge and Stephen Jay Gould in 1972. It views evolution as a series of episodically branching speciations superimposed on long intervals of species stability (called a "stasis"). The idea is reminiscent of earlier ideas on the alternation of times of slow evolution with times of rapid species "radiation." All such concepts depend on whether the changes in morphology of fossils in presumed sequences of ancestors and descendants correctly reflects the rate of genetic change. Although this cannot be proven, it seems reasonable that the rate of change in a given lineage of organisms should not be constant, but should vary between slow and fast, presumably in response to changes in climate.
Radiocarbon - (n.)
Carbon-14 (14C), radioactive with a half-life near 6000 years, is used as a tracer for assessment of rates of change and for dating. It is generated in the atmosphere, by interaction of 14N with neutrons in cosmic radiation, and eventually decays back to 14N. The ocean receives 14C at its surface, through exchange of carbon with the atmosphere. Since its deep waters are isolated from the atmosphere, the loss of 14C from decay is not replenished there. Thus, the distribution of radiocarbon in the deep ocean defines the age of deep water masses, their direction and rate of motion, as well as the overall mixing time of the ocean.
Radiometric dating - (n.)
Besides radiocarbon (see entry above), other radioactive isotopes used for dating are isotopes of uranium (U-238, U-235, with half-lives of 4.5 billion yr and 0.7 billion yr, respectively) beryllium (10Be, with a half-life of 2.5 million yr) and potassium (40K, some of which decays to argon-40 and has a half-life of 1.24 billion yr). The long-lived radioisotopes are mainly of interest to geochemists, but can also serve to date long-term climatic trends and events.
Ramanathan, Venkatarathnam -
Indian-born climatologist and a leader in research on atmospheric chemistry and radiation balance. He was one of the scientists who led the INDOEX (Indian Ocean Experiment) expedition, which investigated the impact of pollutants on climate change. He is currently a professor at the Scripps Institution of Oceanography at UC San Diego.
Index: A to F | G to L | M to R | S to Z
Redfield, Alfred -
(1890-1983): American oceanographer. He made major contributions to the understanding of the chemistry and fertility of the ocean. In particular, he is known for establishing the major patterns of composition in phytoplankton and demonstrating that the ratios of the main elements in marine organic matter are similar to those in seawater. Redfield wrote on physical oceanography, including tides, and he also wrote on the effects that deep circulation in the oceans has on the major patterns of nutrient chemistry of the ocean.
Reid, Joseph L. -
Physical oceanographer at Scripps Institution of Oceanography, UC San Diego. He conducted systematic mapping of the properties of the ocean including temperature, salinity, density, oxygen, phosphate, nitrate, and silicate distributions. He then constructed the motions of ocean water at the different depth levels from the distribution of these properties and made contributions toward understanding the great asymmetry in water mass properties between Pacific and Atlantic ocean basins.
Reservoir - (n.)
In geochemistry, a reservoir is the mass of an element (such as carbon) or a compound (such as water) within a defined “container” (such as the ocean or the atmosphere or the biosphere). The definition is arbitrary, in principle, but may coincide well with actually existing bodies on Earth (such as the ocean). Reservoir properties are “size” and “reactivity,” with the latter given as the ratio of input to size.
Residence Time - (n.)
In geochemistry, it is the average time spent by an atom or molecule with the reservoir, between the time it entered and exited it. Residence time is calculated by dividing the reservoir size by the input (or the output).
Revelle Buffer Factor - (n.)
The "buffer factor" compares the sensitivity of the two reservoirs, the ocean and the atmosphere, in their abilities to a change in their total carbon dioxide content. The value of the factor depends on the extent to which equilibrium with carbonate sediments has been achieved in a given situation. In a now-famous article published in the journal Tellus in 1957, Revelle and Suess applied previous scientists’ work with their buffer factor to calculate the amount that CO2 would increase over the century, and they expressed concern that “human beings are now carrying out a large-scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in future.” The "buffer factor" was also discovered and discussed independently by a scientist named G.N. Plass.
Revelle, Roger R. -
(1909-1991): American geologist and geophysicist. He was a professor at the University of California, co-founder of the UC San Diego campus, director of Scripps Institution of Oceanography (SIO) from 1950-1964, and director of the Institute for Population Studies at Harvard from 1964-1976. He led SIO into world-wide ocean exploration using an expanding fleet of ocean-going ships. In the 1950’s Revelle recognized the importance of studying the Earth’s carbon cycle and the impact of the emission of carbon dioxide by the activities of a growing human population, a process that he described as a "large-scale one-time geophysical experiment" with "the entire planet as laboratory."
Rossby, Carl-Gustaf Arvid -
(1898-1957): Swedish-American meterologist. He studied the wind field of the upper atmosphere using balloons and established circumpolar westerly winds at high altitudes in the polar front zone. When these winds are strong they cause a familiar sequence of cyclones and anticyclones in high temperate latitudes. However, when these winds are weak polar air can penetrate into low
latitudes (i.e. jet stream control). His name is associated with “Rossby waves,” the circumpolar sinusoidal air currents found around a sequence of high and low pressure centers and commonly pegged on the Icelandic and Aleutian low-pressure areas.
Rubbish - (n.)
A term applied by some British philosophers (e.g. Bertrand Russell) to statements resulting from wishful or fuzzy thinking in scientific discussion (i.e. statements without scientific merit). To detect rubbish, it is useful to ask whether the purportedly scientific statement is based on goal-oriented thinking or disinterested scientific analysis and whether it is in any way useful in guiding further research or action. Both overemphasis on the uncertainty of a scientific theory (e.g. evolution) and the neglect of uncertainty (e.g. possible effects of global warming) can easily result in rubbish. Common candidates are statements offering a simple solution to complex problems (when correct, these are called "breakthroughs"). Other candidates are statements predictable from circumstances. For example, a study by the "Good-Smokes Institute" might come up with the finding that the pleasures of smoking greatly outweigh the potential costs in terms of health risks. Likewise, a study funded by the "Coal-Forever Research Institute" might be expected to discover that the use of coal has many proven benefits and comparatively few proven drawbacks.
Index: A to F | G to L | M to R | S to Z